Fork lift truck with shiftable ballast



Dec. 8, 1959 Y B. H. LOCKE FORK LIFT TRUCK WITH SHIFTABLE BALLAST Filed June 13, 1958 f A/VE/VTUR This invention relates to shiftable ballast means incorporated in conventional fork lift trucks that normally are maneuvered on wheels and have vertically operative lifting forks and manual control means therefor which are normally controlled by an operator who either sits or stands on the truck during the maneuvering thereof. The object of the invention is to provide a ballast that can be shifted by either manual control or by automatic control to effectively balance the truck in overcoming abnormal overbalance encountered in lifting material on the forks to relatively high levels, especially when the truck is on a down grade, whereat the tipping moment encountered is greatly augmented by the forks extending out beyond the front end of the truck, which is the conventional location thereof.

I conceive to provide a movable ballast that can be shifted either by manual control means or by automatic control means rearward of the truck to counterbalance a forward overhung load, such as described above, and thereby prevent any further tipping of the truck should the truck tip to a predetermined angle of forward incline when lifting a load.

It is not my conception to improve the present mechanisms of fork lift trucks, but rather to improve the stability of the truck by providing a shiftable ballast therefor for reasons set forth above and thereby increase the utility of the truck for reasons that heavier loads can be lifted to greater heights and the truck can be maneuvered on greater inclines without tipping forward, all due to the ballast being shifted rearward by either manual control means or by automatic control means should the truck tip to a predetermined angle. In the accompanying drawing:

Figure 1, is a side elevation of a conventional fork lift truck enbodying my shiftable ballast means.

Figure 2 is a plan view of the same.

Figure 3 is a rear elevation of the same.

Figure 4 is an enlarged schematic view of the ballast control switch and control valve.

The drawing shows my shiftable ballast means incorporated in a conventional fork lift truck structure which can be briefly described. The chassis of the truck is equipped with rear wheels 11 and front wheels 12 either pair of which could be maneuverable and controlled by a steering wheel 13. Forks 14 are slidably mounted in a vertical structure 15 mounted on the front of the chassis 10. A hydraulic cylinder, not shown is provided to raise and lower the forks and a hydraulic cylinder, indicated at 16, is utilized to tip the guide structure 16 within the limits designated by dotted lines 17.

The lifting structure can be of a so-called single lift structure or it could be a telescope lift structure, both types of structure being common in the art.

A motor, not shown, being either electric or gasoline is mounted on the chassis to drive the truck and a hand brake 18 is provided to restrain the trucks movement if desired. A suitable operators seat 9 is generally protes Patent vided on the chassis although in some forms of trucks the operator is required to stand.

A hydraulic pumping unit, not shown, is provided on the chassis and is driven by the trucks power source to supply hydraulic pressure to actuate the various cylinders required to perform the conventional fork truck operation. All of the above described fork lift truck structure is common in the art and thus it is deemed unnecessary to show the same in detail especially since no improvement therein is to be claimed herein.

My conception is to mount a truck body 19 to slide rearwardly on the chassis 10, in ways 20, which can house storage batteries, designated by dotted lines 21, in the case of an electric powered truck, and a suitable weighted ballast, as indicated by dotted lines 22. Storage batteries are inherently heavy and act as a substantial ballast and the additional ballast is positioned at the rear of the body whereat it becomes most efiective.

A hydraulic cylinder 23 having its main end attached to the chassis 10 at 24 and its rod end attached to the body 19 at 25' is provided to effect the sliding of the body 19 on the chassis 10. The action of cylinder 23 is controlled by a rotatable mounted mercury switch 26, mounted on chassis 10 within reach of the operator, through the medium of a solenoid operated 4-way valve 27. The arrangement of the switch and the valve is shown schematically in Figure 4.

When the switch 26 is rotated to incline the mercury container tube 28 toward the rear of the truck as shown in Figure 4, the mercury closes a circuit 29 which causes actuation of the 4-way valve in the direction to cause oil under pressure to flow to the end 3t of the cylinder 23 and thereby retain the body 19 inwardly against the drivers seat 9, as shown in full lines.

However, should the truck be tipped forward, by an overbalancing load on the forks, sufiiciently to cause the mercury to flow to the other end of the tube 28, circuit 31 would become closed and circuit 29 will become opened and the 4-way valve 27 will be actuated to cause oil to flow to the other end 32 of cylinder 23 and simultaneously allow the oil to exhaust from the end 30. This will cause the body 19 to be moved rearwardly of the truck, as shown in dotted lines 33, and thereby augment the counterbalance effect of the ballast until the truck is righted again. The allowable angle of tip for the truck can be predetermined and the mercury switch can be set accordingly.

The operator can manually rotate the switch 26 by means of a handle 34' at any time to cause the ballast to move rearwardly whenever he feels additional ballast is needed. However, it is obvious that the operator would retain the body inward when possible so as to facilitate maneuvering the truck especially in close quarters. He would only utilize the additional ballast feature when lifting a load high above the truck or when lifting an abnormally heavy load.

Conventional handles 35 that control the lifting and tilting of the forks are provided. Also, pedals, not shown, are provided to control the speed and the braking of the truck, as is common practice in the art.

I do not wish to be confined to the exact details set forth as the same are susceptible of modification within the spirit and scope of the invention set forth.

I claim:

1. A fork lift truck comprising two main parts, a maneuverable chassis mounted on wheels and a slidable body mounted on said chassis, lifting forks mounted on the front of said chassis, ballast means mounted on said body, normal hydraulic power means to maneuver said chassis and to raise and lower said forks, power means to move the slidable body comprising a hydraulic cylinder connected intermediate said chassis and said body and actuated by oil pressure, supplied by a pumping unit on the truck, passing through a valve that is controlled by an adjustable operative level sensing switch having propensity to actuate when inclined mounted on the truck and disposed to be actuated by a tipping of the truck.

2. A fork lift truck comprising a maneuverable chassis mounted on wheels and a ballast carrying body mounted on said chassis to slide rearwardly thereon, lifting forks mounted to slide vertically in guide structure mounted on the front of said chassis, normal hydraulic power means to maneuver said chassis, normal hydraulic power means to actuate said lifting forks, power means to move the ballast carrying body rearward of said chassis to increase the effect of the ballast in righting the truck whenever the same tends to tip forward due to a load being lifted on the forks comprising a hydraulic cylinder connected intermediate the chassis and the ballast carrying body and actuated by oil pressure, supplied by a pumping unit on the truck, passing through a valve controlled by an adjustable switching mechanism having in combination a manual actuating means and a level sensing control means.

3. A maneuverable fork lift truck mounted on wheels, lifting forks extending outwardly at the front end of said truck and slidably mounted in guide structure attached to said truck, structure on said truck supporting ballast to stabilize the truck when lifting material, the last said structure being disposed to be moved rearward of the truck, automatic means to move the last said structure rearward when the truck tips forward to a predetermined angle comprising an adjustable preset level sensing switch having propensity to actuate when inclined mounted on the truck to actuate a valve whenever the truck tips to control oil pressure, supplied by a pumping unit on the truck, passing through said valve to a cylinder disposed to effect movement of the ballast supporting structure, normal hydraulic power means on said truck to drive the same and to operate said forks up and down in their guide structure, control means disposed to be manipu lated by an operator of the truck to control said power means and thus the action of the truck.

4. A lift truck comprising a maneuverable chassis supporting overhanging lifting structure on the front end thereof, a ballast carrying structure disposed on said chassis to slide rearwardly thereon to augment the stability of the truck, normal hydraulic power means on the truck to maneuver the same and to actuate the lifting structure, power means to slide the ballast carrying structure to effect balance of the truck whenever it tends to tip forward comprising a hydraulic cylinder connected intermediate the chassis and the ballast structure and actuated by oil pressure, supplied by a pumping unit on the truck, passing through a valve controlled by an adjustable switching mechanism having in combination a manual actuating means and a level sensing control means.

5. A lift truck comprising a maneuverable chassis supporting overhanging lifting structure on the front end thereof, a ballast carrying structure disposed on said chassis to move rearwardly thereon to augment the stability of the truck, normal hydraulic power means on the truck to maneuver the same and to actuate the lifting structure, power means to move the ballast carrying structure to effect balance of the truck whenever it tends to tip forward comprising a hydraulic cylinder connected intermediate the chassis and the ballast structure and actuated by oil pressure, supplied by a pumping unit on the truck, passing through a valve controlled by an adjustable level sensing switch having propensity to actuate when inclined mounted on the truck and disposed to be actuated by a tipping of the truck.

References Cited in the file of this patent UNITED STATES PATENTS 2,504,885 Schreck Apr. 18, 1950 2,759,563 Marnon et al. Aug. 21, 1956 FOREIGN PATENTS 751,269 Great Britain June 27, 1956 

